217 lines
7.2 KiB
C
217 lines
7.2 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <ctype.h>
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#include <string.h>
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#include <assert.h>
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#include <arpa/inet.h>
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#include <netdb.h>
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#include <limits.h>
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#include "helpers.h"
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// UDP server-related mostly lifted from https://cs.nyu.edu/~mwalfish/classes/16sp/classnotes/handout01.pdf
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#define DF_MONTH_LEN 9
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struct Datefields {
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char month[DF_MONTH_LEN]; // TODO numeric indicator?
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int day;
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int hour;
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int minute;
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int second;
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};
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#define MSG_APP_LEN 64 // TODO check max app name length
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struct Message {
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int priority;
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char application[MSG_APP_LEN];
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struct Datefields date;
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};
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void panic(const char* s) {
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perror(s);
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exit(1);
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}
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int parse_priority(char* message, int* priority, int* position) {
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/*
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Given a string that begins with a message something like: <123>foo
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Parse out the number (123) and place it in the passed `priority` int pointer
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The position after the final `>` will be placed in the passed `position` int pointer
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Returns 0 on success or something else on failure
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*/
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// Must have >3 chars to form <x> priority
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if (strlen(message) < 3) return 1;
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// Must start with <
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if (message[0] != '<') return 1;
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char digits[4];
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memset(&digits, '\0', sizeof(digits));
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int num_digits = 0;
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int pos = 1;
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//bool found_priority_end = false; // TODO
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while (pos < 4) {
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if(!isdigit(message[pos])) return 1; // priority must be numeric
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digits[num_digits] = message[pos];
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num_digits++;
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pos++;
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if (message[pos] == '>') {
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break;
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}
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}
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// TODO if escape the loop because pos >= 4, we never found '>'
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if (num_digits == 0) return 1; // empty priority <> ?
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*priority = atoi(digits);
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*position = pos;
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return 0;
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}
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int parse_datefield(char* message, struct Datefields* date, int* position) {
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/*
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Given a message+position pointers, where message + position in a string like:
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May 10 03:09:59 filterlog: 5,,,....
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Parse out the date and place the fields in the passed datefields struct pointer
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Position will be advanced to the character after the parsed data
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*/
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// char month[8];
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// memset(&month, '\0', sizeof(month)); // makes valgrind happy as the above char contains uninitialized memory
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int date_length;
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if(sscanf(message + *position, "%"STR(DF_MONTH_LEN)"s %d %d:%d:%d%n",
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date->month, &(date->day), &(date->hour), &(date->minute), &(date->second), &date_length) != 5) {
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return 1; // Failed to parse all desired fields
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}
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*position += date_length;
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return 0;
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}
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int parse_application(char* message, char* application, int* position) {
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int app_length;
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if(sscanf(message + *position, "%"STR(MSG_APP_LEN)"s%n", application, &app_length) != 1) { // %n not counted in returned field count
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return 1; // Failed to parse all desired fields
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}
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if(strlen(application) < 2) return 1; // Expect at least chars
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application[app_length-1] = '\0'; // Remove the trailing :
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*position += app_length;
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return 0;
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}
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int parse_message(struct Message* result, char* message) {
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/*
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parse a message like:
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<134>May 10 03:09:59 filterlog: 5,,,1000000103,cpsw0,match,block,in,4,0x20,,239,27547,0,none,6,tcp,40,185.216.140.37,24.4.129.164,57159,11111,0,S,3919167832,,1024,,
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Format:
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<priority>VERSION ISOTIMESTAMP HOSTNAME APPLICATION PID MESSAGEID STRUCTURED-DATA MSG
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Assumes null termed string
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*/
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int priority = 0;
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int position = 0;
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if(parse_priority(message, &priority, &position) != 0) return 1;
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result->priority = priority;
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position++; // Now sits on the first character of the ISOTIMESTAMP
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// Parse ISOTIMESTAMP
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// Note: does not parse a full iso timestamp, only the format above
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struct Datefields date;
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if(parse_datefield(message, &date, &position) != 0) {
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return 1;
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}
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result->date = date;
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position++; // position now at beginning of HOSTNAME field
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// Parse APPLICATION
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// filterlog: 5,,,1000000103,cpsw0,match....
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char application[MSG_APP_LEN];
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if(parse_application(message, application, &position) != 0) return 1;
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memcpy(result->application, application, sizeof(application));
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position += 1; // pass over the space
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printf("remaining: '%s'\n", message + position);
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return 0;
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// char msg_remaining[4096];
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// memset(&msg_remaining, '\0', sizeof(msg_remaining));
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// memcpy(msg_remaining, &message[position], strlen(message) - position);
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// printf("'%s'\n", msg_remaining);
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// or
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// memmove(message, &message[position], strlen(message) - position);
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// printf("'%s'\n", message);
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}
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int main(int argc, char** argv) {
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if (argc != 2) {
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fprintf(stderr, "usage: %s <port>\n", argv[0]);
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exit(1);
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}
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// Parse port number to integer
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char* portend;
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unsigned int portl;
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portl = strtol(argv[1], &portend, 10);
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if (portend == NULL) panic("strtol");
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assert(portl < USHRT_MAX);
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unsigned short port = (unsigned short)portl;
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// Create socket
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int sock_fd;
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char msg[4096];
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if ((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
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panic("socket");
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// Set socket options
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int one = 1;
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setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
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// Bind socket
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struct sockaddr_in my_addr, my_peer_addr;
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memset(&my_addr, 0, sizeof(my_addr));
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my_addr.sin_family = AF_INET;
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my_addr.sin_addr.s_addr = INADDR_ANY;
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my_addr.sin_port = htons(port);
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if (bind(sock_fd, (struct sockaddr*)&my_addr, sizeof(struct sockaddr_in)) < 0)
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panic("bind failed");
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socklen_t addrlen = sizeof(struct sockaddr_in);
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while (1) {
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int size_recvd;
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if ((size_recvd = recvfrom(sock_fd, /* socket */
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msg, /* buffer */
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sizeof(msg), /* size of buffer */
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0, /* flags = 0 */
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(struct sockaddr*)&my_peer_addr, /* who’s sending */
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&addrlen /* length of buffer to receive peer info */
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)) < 0)
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panic("recvfrom");
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assert(size_recvd < sizeof(msg)); // messages can't be longer than our buffer
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assert(addrlen == sizeof(struct sockaddr_in));
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printf("Got message: %s\n", msg);
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// TODO should we check that msg[size_recvd] == \0 ?
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// printf("From host %s src port %d got message %.*s\n",
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// inet_ntoa(my_peer_addr.sin_addr), ntohs(my_peer_addr.sin_port), size_recvd, msg);
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struct Message result;
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// printf("XXXsize: %lu", sizeof(result)); // curious how big the struct gets
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//printf("msg[size_recvd] is: %d", msg[size_recvd]);
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msg[size_recvd] = '\0'; // We receive 1 full string at a time
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if(parse_message(&result, msg) != 1) {
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printf("message is valid:\n\tpriority: %d\n\tapplication: %s\n\tDate: %s %d %02d:%02d:%02d\n",
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result.priority, result.application, result.date.month, result.date.day, result.date.hour,
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result.date.minute, result.date.second);
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}
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}
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exit(EXIT_SUCCESS);
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}
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